Vertical powder painting aluminum sections
Widely used in modern construction aluminum extruded profiles with powder polymer coatings. These aluminum profiles particularly high demands on their appearance and durability. The thing is, that the painted surface defects and damage to the aluminum profiles, which are part of large construction and architectural design, not so easy to repair or repaint. At the same time, These profiles are subjected to severe climatic and weather resistant, including, solar radiation, rain and large temperature swings. All of this means, that painted aluminum profiles must maintain its attractive appearance over a long period of very difficult conditions.
Aluminum profiles with powder coating
Therefore, the production of colored aluminum profiles requires the highest possible level of quality powder coating process. This requires a thorough quality control, process both the powder coating, and the finished powder coating aluminum profiles.
A feature of the construction and architectural aluminum is a wide variety of colors of the powder coating. Therefore, powder coating manufacturers should be prepared for frequent changes of paint on its paint lines.
Design of modern buildings require an increased length of aluminum profiles. Until recently, the standard length was aluminum profiles 6 m. Currently, builders are increasingly needed length profiles 7 m, and even 7,5 m, for example, for front struts, which are installed directly on the two floors of the building.
The types of powder coating lines
The choice of powder coating line for each enterprise depends on many factors. These factors include the annual production profiles, dimensions of industrial premises (area, length, height), the number of profiles in batches, color change frequency, the possibility of coloring of products of different sizes and from different materials, and the like.
Regardless of the type lines, each of them should include the necessary technological steps:
- chemical surface preparation of profiles;
- drying of profiles after chemical preparation;
- electrostatic powder coating of profiles;
- powder coating processing in a polymerization oven;
- cooling the profiles after the polymerization oven;
Manufacturers of equipment for powder coating, including, aluminum profiles, They offer various types of painting lines. for instance, the well-known company EUROIMPLANTI (Italy) [1] produces several types of painting lines in various options for performance and equipment layout, taking into account the specific requirements of customers.
Powder coating lines may differ from each other:
- by orientation of aluminum profiles during processing: horizontal and vertical lines;
- by the method of powder spraying - automatic and manual;
- by the method of surface preparation - chromate and chromate-free;
- continuous and with a division into surface preparation and painting itself;
- by arrangement of technological equipment - in one level or in two levels ("compact" lines).
The methods for loading and unloading profiles depend on the type of painting line:
- on continuous automatic lines, profiles are loaded at the beginning of the line (before chemical preparation), but they are discharged already with a ready-made powder coating after processing in a polymerization oven and cooling;
- small lines can have separate stages of chemical preparation in horizontal tanks; at the next stage, the profiles are hung on the conveyor for the actual powder coating.
Vertical powder coating line
The first vertical powder coating lines appeared in Italy back in the 1980s [2]. Therefore, the Italian manufacturer of this equipment have great credibility all over the world. These lines are ideal for large-scale production of aluminum profiles with multiple extrusion presses. These lines can vary in performance, on the conveyor speed, by area, they all consist of interconnected separate modules:
- baseline profiles loading and unloading zone of finished profiles, usually combined in one zone;
- tunnel for chemical surface preparation of profiles;
- drying oven of profiles after chemical preparation before applying powder by spraying;
- a polymerization oven for chemically combining various components of the powder paint into a durable powder coating;
An example of a typical arrangement of a vertical line equipment powder coating aluminum profiles shown in Figure 1.
Figure 1 - The scheme of a typical vertical line powder coating
(EuroFlex line of the Italian company EUROIMPLANTI [2]):
1 - download, 2 - tunnel surface preparation, 3 – drying oven,
4 - powder spray booth, 5 - a polymerization oven, 6 – unloading
Loading profiles
A general view of the loading area is shown in Figure 2. Profiles are supplied to the horizontal table loading zone. One end of each profile previously provided with an opening. In the hole insert a special hook, which is connected to the main conveyor of the line (figure 3). In the course of the conveyor profile is gently raised from its horizontal position to a vertical position. Further, the conveyor carries the profiles of all the working operations of the line - chemical processing, dried, spraying powder and a powder of polymerization.
Figure 2 - General view of the vertical line feed zone
powder coating of aluminum profiles [2]
Figure 3 - System attaching aluminum profiles
on the conveyor of the vertical powder coating line [2]
Tunnel surface preparation profiles
Tunnel chemical preparation of profiles represents a number of separate sections, in the lower part of which there are baths (reservoirs) with various working solutions and water for various stages of washing (figure 4).
Figure 4 - Tunnel chemical preparation
surface of aluminum profiles [2]
Modern tunnels for chemical preparation use a cascade movement of water and solutions from the top of the tunnel downward (Figure 5). The method of cascade flow of water and the solution was allowed to exclude the use of hundreds of nozzles, which have been used previously. This saves electricity, which was spent on numerous pumps, and also to reduce the consumption of chemicals for working solutions. Moreover, reduced maintenance costs for cleaning, adjustment, setting up and replacing multiple spray nozzles [3].
Figure 5 - Cascade system for supplying solutions and flushing water [2]
Oven drying sections
The profiles are located out of the tunnel wet the surface preparation and therefore before application of the powder require thorough drying. So they come in a drying oven, in which the hot air circulates. The air circulation system is arranged in such a way, to quickly dry the moisture from all surfaces of the profiles.
Powder paint spraying cabin
Powder spraying takes place in a special booth (picture 6), which is on 10 to 20 sputter guns. Cab connected to a powder recycling system, that allows you to use a powder with an efficiency of up to 98 % [1, 2].
Figure 6 - Powder paint spraying booth [2]
Sometimes line vertical powder coating include more than one, but two or even three [1] powder spraying booths. In this case, you can speed the transition from one color to another color of paint. While one cabin goes clean for color change, It is running another cabin. This system allows up to 20 color changes per shift (figure 7) [1].
Figure 7 - Change of color for a small batch (6 profiles) yellow
on a vertical line with three spray booths [1]
polymerization oven
Profiles with sprayed powder fed into the polymerization oven. Usually this gas convection or electric infrared. The treatment temperature profiles in the furnace is from polymerization 160 to 210 ° C depending on the type of powder paint, and treatment duration - about 20 minutes.
Unloading of finished profiles
After exiting the curing oven conveyor is ready, but hot enough long profiles by, that upon arrival to the place of unloading, they had time to cool down to normal temperature for manual unloading of the conveyor.
Conclusion
The technology and equipment for the application of powder coating aluminum profiles can have their own characteristics and differences depending on various production conditions. Vertical powder coating line is usually used for fairly large productions. The modular principle of technology and the use of the equipment will allow to take into account all the needs and characteristics of specific manufacturers, are applied powder coatings for aluminum profiles.
Sources:
1. Joseph C. Benedyk – LIGHT METAL AGE, OUR 2006
2. http://www.euroimpianti.ru/sistemy/sistemy-dlya-pokraski-alyuminiya/eurovertical
3. https://www.pfonline.com/articles/quality-italian-style
